The first Zika virus (ZIKV) isolation was made from a monkey in Uganda, and many isolates of ZIKV have been made from the canopy-dwelling mosquito Aedes africanus. Data from these few studies represent the extent of what is currently known about vectors and hosts involved in sylvatic ZIKV circulation. This project seeks to uncover evidence for circulation of ZIKV among bats and mountain gorillas in East Africa. We hypothesize that if sylvatic ZIKV is being transmitted by arboreal mosquito vectors in the forest canopy among non-human primates, then fruit bats congregating at this forest stratification to roost and/or feed on fruits would also be exposed to feeding mosquitoes. For this proposed study, archived blood and/or tissue from 782 bats captured throughout Uganda, including within and around Zika forest, will be screened for ZIKV neutralizing antibody and/or residual viral RNA. Archived blood samples are also available from 32 mountain gorillas from around the Democratic Republic of the Congo / Rwanda border. Serum samples will be screened for neutralizing antibody against ZIKV and closely-related flaviviruses by plaque reduction neutralization (PRNT), and the novel methodology of digital droplet PCR (ddPCR) will be employed for increased sensitivity of detection of residual viral RNA in bat tissues. Utilization of ddPCR in this study also represents a new application of this technology to biosurveillance. These data will be valuable towards investigating potential role of bats as secondary reservoirs of ZIKA in the epicenter of its emergence.